1. Field of the Invention
The present invention relates to methods and apparatus for automatically purging water from irrigation systems.
2. Discussion of Related Art
Irrigation systems installed in regions where cold climate conditions exist can be damaged by freezing of the water contained in the irrigation system and require winterization to prevent this damage. Compressed air is commonly used to force the water out of the irrigation system. Common practice is to hire a contractor who utilizes an industrial grade, engine driven, air compressor with a high flow rating at high pressures and a large volume capacity reservoir to connect to the existing irrigation system. The engine driven air compressor and reservoir are generally large, expensive, and noisy devices pulled by a truck or in the bed of a truck. The contractor must be granted access to the structure to manually turn off the main water supply. The air compressor and reservoir are then connected to the existing irrigation system outside the structure. The contractor then steps through each irrigation zone, blowing air through the selected zone forcing the water out through the sprinkler heads, drips, or misters. The contractor observes each zone and when only air is being emitted from the sprinkler heads, drips, or misters, they manually move to the next zone.
It is common knowledge to step through the zones one at a time to reduce the amount of air required to purge the water. Also, irrigation controllers don't allow more than one zone to be on at a time. Therefore to open more than one zone valve at a time would require the contractor to find each zone valve box located around the structure and manually actuate each zone valve. This is time consuming and many times the remote valve boxes are covered by landscape material and difficult to locate. By default, most contractors just step through each zone using the irrigation controller.
It is well known that a home owner can achieve similar purge results with a smaller air compressor and reservoir but take significantly longer to run and may require multiple cycles per zone. Both methods are labor intensive and require the operator to work outside in uncomfortable, cold climate conditions. Both the contractor and homeowner have to be diligent in observing air pressures so as to not damage the irrigation system by exceeding the rating of the piping, the valves, or the sprinkler heads.
Depending on weather conditions and the time of year, the irrigation system user must estimate when they want the system purged of water. If they err on the conservative side and purge the system too soon, they may have landscape damage if warm, dry weather returns. If they err on the aggressive side and purge the system too late, they may have irrigation system freeze damage. Once purged, they are hesitant to turn the water back on due to the inability to have it purged again that same day and the expense involved.
New landscaping and existing trees and shrubs require watering in cold dry months. It becomes cumbersome and time consuming to pull out the garden hose and water the landscaping during cold weather. The landscaping can be easily watered using the irrigation system then immediately followed by an automatic purge of the system.
Bailey in U.S. Pat. App. No. 2011/0079654, teaches a purging system that is mainly flow based over a given amount of time. It utilizes an expensive, complicated air supply pump and feedback system where it maintains a consistent pressure in the zone by adjusting the speed of the air supply. Variable speed motors require expensive controllers. Also, in order to monitor the pressure in the system, a more expensive pressure sensor must be used to provide continuous pressure feedback. Even with only one zone open at a time, the flow based systems require large capacity flow pumps, with a very high cubic-feet per minute capability, to reach a stable pressure once the water has been forced from the zone. The flow rate of air that can be emitted from a sprinkler head is greater than the flow rate of water that can be emitted. Therefore, to reach a stable air pressure, large flow rates must be maintained and seem overkill for the simple task being accomplished. Also, Bailey has stated that the necessary outputs of the air source may increase if there is no air reservoir to assist with the purging.
Irrigation systems are designed to operate with water pressures up to 80 psi. The purge system that quickly discharges compressed air from an air reservoir, known as the pressure purge method, staying below pressures of 80 psi, has proven to be the most economical and accommodative to the widest range of irrigation piping systems and air compressors. A successful irrigation purge system should accommodate unique irrigation systems with varying number of zones, unequal pipe lengths, different pipe diameters, different number and variety of sprinkler heads or outlets, and varying degrees of slope of the terrain being irrigated. Also, users who already own a suitable air compressor will prefer to use it in conjunction with the purge system.
There is a need in the art for methods and apparatus for automatically purging water from irrigation systems such as an irrigation purge system that can utilize a common, traditional air compressor on unique and diverse irrigation piping in a cost effective manner, protect the system from high pressure conditions, be fully automatic, know when each zone has been purged of water, handle multiple error conditions, maintain water valve settings without consuming power and during a power loss or unplugged condition, and seamlessly integrate with all irrigation controllers.